/*
 * Copyright (C) 2018 Donlon.
 *
 * 2018秋季C语言练习题（4）
 * http://10.105.242.83/contest/484/
 *
 * A. 分制转换
 */

#include <stdio.h>

int main() {
  int grade;
  scanf("%d", &grade);

  char grade_char = 0;

  if (90 <= grade) {
     grade_char = 'A';
  } else if (80 <= grade) {
     grade_char = 'B';
  } else if (70 <= grade) {
     grade_char = 'C';
  } else if (60 <= grade) {
     grade_char = 'D';
  } else  {
     grade_char = 'E';
  }

  printf("%c", grade_char);
}
